This relates generally to imaging systems and, more particularly, to imaging systems with stacked image sensors.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imaging systems (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensitive element such as a photodiode that receives incident photons (light) and converts the photons into electrical signals.
In a typical arrangement, an imaging system includes a single image sensor with a single array of image sensing pixels. It can be challenging, however, to detect different types of electromagnetic radiation using a single image sensor. For example, it can be challenging to design a single image sensor that can detect and distinguish between visible light and infrared light. Some image sensors include pixel arrays with visible imaging pixels that are sensitive to visible light and infrared pixels that are sensitive to infrared light. However, because these imaging pixels are fabricated in a single image sensor die, it can be difficult to fabricate the image sensor die using materials that are optimized for both visible and infrared imaging.
Some imaging systems include multiple image sensors, each having a separate array of image sensing pixels that is optimized to detect a particular type of electromagnetic radiation. This type of system typically includes multiple image sensor dies arranged laterally adjacent to one another, consuming valuable real estate in an electronic device and adding undesirable bulk to the electronic device.
It would therefore be desirable to provide improved imaging systems for detecting different types of electromagnetic radiation.